Maybe not the best example to use on these forums but Sterling had something similar with competition.
Sané and Nolito arrived, what does that mean for Sterling people asked. Is he going to get games and progress? Ends up as 1st choice winger.
Bernardo arrived, what does that mean for Sterling people asked. Is he going to get games and progress? Ends up as 1st choice winger and key player in title success.
Mahrez arrived, what does that mean for Sterling people asked. Is he going to get games and progess? Ends up as 1st choice winger and has his best season ever to date.
Stones has never really had anyone to truly threaten his position long term, even with his injuries. Kompany was never reliably fit, Otamendi was never reliably reliable, and Laporte played on the other side. Fernandinho at CB and 19/20 year old Garcia were never going to truly make him feel threatened either. There was no true motivation.
Now he has to step up because we have 3 other CBs that will happily keep him out of the team for a long time if he doesn't buck up. And he knows that if he leaves City on a low it'll be a long time to get back up to the top for him.
Hopefully he keeps this up because the team needs personalities like that. Pep didn't compliment his balls by accident! We're at our best when we have a bunch of players that can step up when things look rough for them. Aguero, Walker, and Kompany are three of the best in my experiences, and Sterling does better than most. Much better than the likes of Hart or Sané that slowly wilted at the first threat of long term competition.